Lift assembly systems and methods

Abstract

A lift assembly comprising an article to be raised and lowered, a cable coupled to the article and defining a longitudinal axis, a power mechanism coupled to the drive element, a drum powered by the power mechanism, a cable keeper biasing the drive element toward the drum, a keeper shaft providing lateral movement of the cable keeper, and an encoder mounted for rotation with the keeper shaft. The encoder provides information regarding the position of the article. The lift assembly can also include a load cell assembly including a load cell housing, a load cell member contacting the drive element and movable relative to the load cell housing, and a load cell sensor coupled to the load cell member and operative to provide an output corresponding with a load on the drive element. The load cell member can be mounted for movement laterally relative to the longitudinal axis.

The invention claimed is: 
     
       1. A lift assembly comprising:
 an article to be lifted between a lowered position and a raised position; 
 a flexible drive element coupled to the article and defining a longitudinal axis; 
 a power mechanism coupled to the drive element; 
 a drum powered by the power mechanism and dimensioned to facilitate winding of the drive element onto the drum; 
 a cable keeper providing a force on the drive element to bias the drive element toward the drum; 
 a keeper shaft coupled to the cable keeper to provide movement of the cable keeper laterally relative to the longitudinal axis; and 
 an encoder mounted for rotation with the keeper shaft, wherein the encoder provides information regarding the position of the article from the lowered position to the raised position. 
 
     
     
       2. The lift assembly of  claim 1 , wherein the power mechanism includes a drive shaft, wherein the encoder is a first encoder, and wherein the assembly further comprises a second encoder mounted for rotation with the drive shaft, wherein the first encoder rotates at a slower rate than the second encoder as the article is moved between the lowered and raised positions; and wherein the first and second encoders provide information regarding the position of the article from the lowered position to the raised position. 
     
     
       3. The lift assembly of  claim 2 , wherein the first and second encoders are mechanical encoders. 
     
     
       4. The lift assembly of  claim 2 , wherein the first and second encoders are absolute encoders. 
     
     
       5. The lift assembly of  claim 1 , further comprising a load cell assembly including:
 a load cell housing; 
 a load cell member contacting the drive element and movable relative to the load cell housing; and 
 a load cell sensor coupled to the load cell member and operative to provide an output corresponding with a load on the drive element. 
 
     
     
       6. The lift assembly of  claim 5 , wherein the flexible drive element comprises a cable. 
     
     
       7. The lift assembly of  claim 5 , wherein the load cell member comprises a roller. 
     
     
       8. The lift assembly of  claim 5 , further comprising a keeper bar positioned adjacent the load cell member. 
     
     
       9. The lift assembly of  claim 5 , wherein the load cell member is coupled to a pivot block, and the pivot block is coupled to the load cell sensor. 
     
     
       10. The lift assembly of  claim 5 , wherein the load cell member is mounted for movement laterally relative to the longitudinal axis. 
     
     
       11. A lift assembly comprising:
 an article to be lifted between a lowered position and a raised position; 
 a flexible drive element coupled to the article and defining a longitudinal axis; 
 a power mechanism coupled to the flexible drive element; 
 a drum rotatable by the power mechanism to wind the flexible drive element about the drum; and 
 a load cell assembly positioned in contact with the drive element, the load cell assembly comprising:
 a load cell housing; 
 a first load cell member contacting a portion of the drive element between the drum and the article to be lifted, wherein the first load cell member is movable relative to the load cell housing; 
 a second load cell member contacting the drive element at a position spaced from the first load cell member; and 
 a load cell sensor coupled to the first load cell member and operative to provide an output corresponding with a load on the drive element. 
 
 
     
     
       12. The lift assembly of  claim 11 , wherein the flexible drive element comprises a cable. 
     
     
       13. The lift assembly of  claim 11 , wherein the first load cell member comprises a roller. 
     
     
       14. The lift assembly of  claim 11 , further comprising first and second keeper bars positioned adjacent the first and second load cell members, respectively. 
     
     
       15. The lift assembly of  claim 11 , wherein the first load cell member is coupled to a pivot block, and the pivot block is coupled to the load cell sensor. 
     
     
       16. The lift assembly of  claim 11 , wherein the first load cell member is movable laterally relative to the longitudinal axis.